The present invention generally relates to ignition systems and, more particularly, to an ignition detection system for use prior to and/or during a lift-off/take-off sequence of a rocket powered spacecraft/aircraft.
Propulsion systems and/or rocket engines have traditionally been utilized in a variety of applications ranging from space shuttle and rocket missions to missile launching applications. These propulsion systems and/or rocket engines ideally possess safe and dependable systems for controlling their ignitions and accompanying launches. In particular, safe and reliable engine ignition is particularly important in spacecraft applications involving the launch of manned spacecrafts such as liquid fueled rockets and space shuttles.
These propulsion systems and/or rocket engines generally have a combustion chamber that releases an exhaust plume from the exhaust nozzle(s) of each engine. These exhaust plumes generally include heat and flames, among other distinguishing features. A failure to properly ignite the fuel utilized for providing a pilot light and/or the main fuel in the combustion chamber may result in one or more engines malfunctioning and the spacecraft lacking the lift needed for launch, potentially resulting in the loss of lives and/or damage to the spacecraft and/or launch pad. Further, an incorrect or failed ignition may be symptomatic of one or both fuel and oxidizer from the spacecraft being dumped onto the launch pad. Any subsequent ignition of this fuel/oxidizer could potentially result in a catastrophic event.
One conventional procedure of engine ignition detection includes stretching wires across each engine exhaust nozzle. The plume of exhaust is intended to burn away and generally completely sever each of the wires, thus indicating that each of the engines are sufficiently ignited. Potential problems with this type of an ignition detection system include, but are not limited to, wind breaking the wires that span across the exhaust nozzle(s) indicating successful ignition before launch is even attempted. This would yield a potentially xe2x80x9cfalse positivexe2x80x9d signal if ignition did not in fact occur. This type of ignition detection system can also result in xe2x80x9cfalse abortxe2x80x9d signals as well. That is, there may be instances where even a proper ignition may fail to completely burn through or otherwise sever the wires. This false xe2x80x9cfailedxe2x80x9d ignition signal can cause the launch of an entirely satisfactory rocket to be aborted.
The present invention is generally directed to the detection of engine ignition. More specifically, the methods and apparatus of the present invention are generally directed to the detection of liquid-fueled rocket engine ignition of a spacecraft/aircraft. A preferred application of the present invention may be in the use of ignition detection systems for launch vehicles.
A first aspect of the present invention is embodied in a method for operating an engine (e.g., a liquid-fueled rocket engine). The method generally includes initiating an ignition sequence that includes at least a first ignition stage and a second ignition stage for the engine. The method further includes monitoring first ignition stage electromagnetic spectra and second ignition stage electromagnetic spectra at least during a time corresponding with the first and second ignition stages, respectively. A first relay is generally activated if the first ignition stage electromagnetic spectra reach(es) a first predetermined threshold within a first predetermined timeframe. Correspondingly, a second relay is generally activated if the second ignition stage electromagnetic spectra reach(es) a second predetermined threshold within a second predetermined timeframe. xe2x80x9cReachesxe2x80x9d, in relation to the first and second predetermined thresholds, encompasses meeting a certain value, exceeding a certain value, or both. In the event that either relay is not activated within the corresponding predetermined timeframe, the ignition sequence is generally terminated.
Various refinements exist of the features noted in relation to the subject first aspect of the present invention. Further features may also be incorporated in the subject first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. For instance, the first ignition stage electromagnetic spectra may include ultraviolet, visible, and/or infrared light rays but may be most intense in the visible. Accordingly, this first aspect may include monitoring electromagnetic spectra within a wavelength range of about 400 nm (visible blue light) to about 700 nm (visible red light). The first ignition stage electromagnetic spectra may thereby encompass a range of wavelengths, although the first ignition stage electromagnetic spectra may also be a single, individual wavelength. The second ignition stage electromagnetic spectra may include ultraviolet, visible, and/or infrared light rays but may be most intense in the infrared. Thus, this first aspect of the present invention may include monitoring electromagnetic spectra within a wavelength range of about 7.0xc3x97102 nm up to about 3.0xc3x97105 nm, and in some embodiments, a wavelength range of anywhere between 7.0xc3x97102 nm and 7.8xc3x97102 nm up to about 1.0xc3x97105 nm. As with the first ignition stage electromagnetic spectra, this second ignition stage electromagnetic spectra may also encompass a range of wavelengths or may merely include a single, individual wavelength.
Generally, one or both of the first and second ignition stage electromagnetic spectra in the case of the first aspect may be emitted by an ignition of at least one of hypergolic fuel and kerosene. In one embodiment, a mixture of hypergolic fuel and liquid oxygen is utilized in the first ignition stage, while a mixture of liquid oxygen and kerosene is utilized in the second ignition stage. In this case, the first ignition stage electromagnetic spectra may be visible electromagnetic spectra that are monitored for purposes of the first ignition stage, while the second ignition stage electromagnetic spectra may be infrared electromagnetic spectra that are monitored for purposes of the second ignition stage. xe2x80x9cHypergolxe2x80x9d (also known as hypergolic fuel) refers to a liquid fuel or propellant that generally ignites in a substantially spontaneous fashion upon contact with an oxidizer. An xe2x80x9coxidizerxe2x80x9d generally includes oxygen and/or any compound that spontaneously evolves oxygen either at ambient temperature and/or upon exposure to heat. These oxidizers (or oxidizing materials) generally react vigorously (i.e., can cause and/or support ignition/combustion) when mixed with reducing materials (such as liquid hydrocarbons, hypergolic fuels, cellulose-based organic compounds, and/or other appropriate organic compounds).
First and second ignition stage electromagnetic spectra that generally are associated with the first and second ignition stages of the ignition sequence may be monitored in this first aspect of the invention. In this first aspect, the process of monitoring electromagnetic spectra can include using spectrometers, radiometers, and the like, some of which may optionally be equipped with filters. In one embodiment of the first aspect, photons of the first and second ignition stage electromagnetic spectra are converted to electrical signals (i.e., photo-electrons), and these electrical signals are then monitored for the first and second predetermined thresholds (e.g., first and second voltage thresholds, respectively) as well as if/when in the timeframe of the launch sequence these thresholds are reached. These electrical signals may be amplified (e.g., using an appropriate amplifier) to improve one or more aspects associated with the monitoring of the same to identify the existence of first and and/or second ignition stage electromagnetic spectra that reach the corresponding predetermined thresholds.
As previously mentioned, the first relay can be activated upon the first ignition stage electromagnetic spectra meeting or exceeding a first predetermined threshold at a first predetermined time slot in the ignition sequence in the case of the first aspect. In one embodiment of the first aspect in which the first ignition stage electromagnetic spectra that are monitored include visible light (e.g., electromagnetic spectra having wavelengths between about 400 nm and about 700 nm), the first predetermined threshold may be established within a range of about 1000 arbitrary power units above a background. Herein, xe2x80x9cbackgroundxe2x80x9d is generally determined by looking at an xe2x80x9cempty, featurelessxe2x80x9d sky (i.e., sky generally having no clouds or sun in the field of view) and by making a measurement of the brightness of the sky. This measurement is generally defined as the background. Accordingly, the particular threshold may be chosen to be up to 1000 times brighter than the background measurement. Once the monitored visible light meets or exceeds the first predetermined threshold and occurs within the first predetermined timeframe, a first relay can be activated to indicate that the monitored visible electromagnetic spectra are at an appropriate level and occurred at an appropriate time (i.e., indicate a proper ignition of the subject fuel) for lift-off/takeoff. Similarly, the second relay can be activated upon the second ignition stage electromagnetic spectra meeting or exceeding a second predetermined threshold and occurring in within the second predetermined timeframe. Continuing with the above-noted embodiment where the second ignition stage electromagnetic spectra that are monitored include infrared light (e.g., electromagnetic spectra having wavelengths between about 1.0xc3x97103 nm and about 1.0xc3x97105 nm), the second predetermined threshold may be established within a range of about 1000 arbitrary power units above background. Once the monitored infrared light meets or exceeds that second predetermined threshold, and occurs within the second predetermined time slot, a second relay can be activated. In one embodiment, a xe2x80x9cgoxe2x80x9d signal may now be generated to indicate that the monitored first and second ignition stage electromagnetic spectra are at appropriate levels and have occurred at the appropriate times (i.e., indicate a proper ignition of the particular fuel(s)) for liftoff/takeoff.
Preferably, with regard to this first aspect of the invention, both the first and second relays must be activated to proceed with the ignition sequence. In other words, activation of both the first and second relays preferably indicates that engine conditions are appropriate to continue with the ignition sequence. This first aspect not only generally requires that the first and second relays be activated to proceed with the ignition sequence, but that both the first and second relays are activated within the corresponding predetermined timeframes of the launch sequence. In some embodiments, the first and second relays may be required to be activated within a predetermined time of each other. Exactly where in the launch sequence the particular stage one and stage two ignition timeframes occur may be dependent upon factors such as, but not limited to, the type of rocket engine utilized. These first and second predetermined timeframes may be determined by observation/analysis of, for example, engine hot fire tests and/or test launches. As an example of this first aspect, the first predetermined timeframe of the first ignition stage spectra for Rocketdyne MA-5 engines can generally be established in the ignition sequence to be within a range of about Txe2x88x922.79 seconds to about Txe2x88x923.40 seconds. Herein, xe2x80x9cT-x secondsxe2x80x9d generally refers to amount of time xe2x80x9cxxe2x80x9d prior to lift-off/takeoff (T) of the flight vehicle. So, for example, xe2x80x9cTxe2x88x922.79xe2x80x9d seconds generally refers to about 2.79 seconds prior to the time the launch vehicle is supposed to liftoff/takeoff. Continuing with the example, the predetermined time of the second ignition stage spectra can generally be established to be within a range of about Txe2x88x921.59 seconds to about Txe2x88x922.20 seconds. In other words, the amount of time that passes between the first and second relays being activated, at least with regard to Rocketdyne MA-5 engines, may generally be no more than about 1.81 seconds, or else the ignition sequence may be aborted. Thus, the first and second relays being activated within the predetermined timeframes associated with the first aspect generally indicates that the ignition sequence may proceed. In one embodiment, an ignition shutdown signal may be issued in response to at least one of the first and second ignition stage electromagnetic spectra not reaching (i.e., meeting or exceeding) the respective first and second predetermined thresholds, and/or not occurring at or within the corresponding first and/or second predetermined timeframes. In other words, if one or both the first and second relays are not activated or activated at the wrong time, an xe2x80x9cabortxe2x80x9d signal of sorts may be issued. In another embodiment, the activation of the first and second relays within the required predetermined time of each other may be utilized to initiate a xe2x80x9cgoxe2x80x9d signal for proceeding with the ignition sequence.
The first aspect of the invention can be utilized to detect ignition of engines that can be found in various types of what may be characterized as flight vehicles such as launch vehicles, airplanes, rockets, missiles, space shuttles, and satellites. In one embodiment of the first aspect, direct physical contact between ignition detection equipment and the aircraft is not required, such that there is not contact between any ignition detection equipment and the aircraft. In other words, the equipment that is utilized to carry out the process of ignition detection in this embodiment is generally separated from and does not interface with any portion of the aircraft. Generally, each of the various features discussed herein in relation to one or more of the described aspects of the present invention may be utilized by this first aspect of the present invention as well, alone or in any combination.
A second aspect of the invention is embodied in a launch system that includes an ignition detection system and a launch vehicle having at least one engine. The ignition detection system of this second aspect includes a camera assembly (such as a spectrometer or radiometer), a fiber optic input cable, and a control assembly. The camera assembly generally has an input area and an output area. The fiber optic input cable generally has an attachment end optically connected to the input area of the camera assembly and a hot end disposed opposite the attachment end. Accordingly, the hot end of the fiber optic input cable is generally disposed at least within an optically effective distance of the engine. Herein, an xe2x80x9coptically effective distancexe2x80x9d refers to a distance which allows detection of electromagnetic spectra representative of an ignition of the engine. Ideally, both the camera assembly and the fiber optic input cable are free from direct contact with the launch vehicle. In other words, the camera assembly and the fiber optic input cable are preferably separated from and avoid interfacing with any portion of the launch vehicle, and more particularly the engine. The camera assembly is generally operatively interconnected (e.g., via a copper wire) with the control assembly so that signals indicative of the electromagnetic spectra may be passed/conveyed between the camera assembly and the control assembly.
Various refinements exist of the features noted in relation to the subject second aspect of the present invention. Further features may also be incorporated in this second aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. For instance, the ignition detection system can be mounted on a launch pad. In one embodiment of the second aspect, the ignition detection system (or at least the control assembly and the camera assembly) is designed and configured to effectively avoid structural damage during provision of the ignition detection function, thus making the ignition detection system of the second aspect reusable for detection of multiple, spaced-in-time ignitions for multiple launch vehicles (e.g., from multiple launches). For example, in the case of an explosive missile, the ignition detection system associated with the second aspect would not be a component of that missile. As another example, in the case of booster rocket for propelling an appropriate spacecraft into outer space, the ignition detection system associated with the second aspect would not be integral with the booster rocket, thus avoiding loss of and/or significant damage to the ignition detection system after the booster rocket has served its purpose and been dissociated from the spacecraft it propelled into outer space.
The control assembly (e.g., a dual setpoint controller of the control assembly) of the ignition detection system utilized by this second aspect may be programmed with a first predetermined threshold that is associated with first electromagnetic spectra and a second predetermined threshold that is associated with second electromagnetic spectra. Moreover, the control assembly (e.g., a programmable logic controller of the control assembly) generally may be programmed with one or more time thresholds corresponding to an acceptable timeframe for the first ignition stage, an acceptable timeframe for the second ignition stage, and/or an acceptable time duration between the camera assembly detecting that the first predetermined threshold and the second predetermined threshold have been reached. As such, the various features discussed above in relation to the first aspect may be implemented in this second aspect as well.
The camera assembly utilized by the second aspect can include a variety of components. Generally, any camera assembly capable of monitoring and/or detecting the electromagnetic spectra described herein may be appropriate for use in the ignition detection system associated with the second aspect. In one embodiment of the subject second aspect, the camera assembly may include at least one camera having one or more of: 1) a filter which substantially allows only specified wavelengths of electromagnetic spectra to pass through the filter; 2) a focusing optic which at least partially condenses the electromagnetic spectra; and 3) a signal amplifier for intensifying photo-electron signals corresponding to the electromagnetic spectra. In another embodiment, the camera assembly associated with the second aspect includes first and second cameras. In this case, the first camera may generally detect first electromagnetic spectra (e.g., a range of wavelengths or a single, individual wavelength), and the second camera may generally detect second electromagnetic spectra (e.g., a range of wavelengths or a single, individual wavelength). In a preferred embodiment of the second aspect, the first camera can generally detect visible light wavelengths, and the second camera can generally detect infrared light wavelengths. In the case where there are first and second cameras, the fiber optic input cable can have a first fiber optic operatively interconnected with a first input of the first camera for taking in spectral data and/or conveying it to the first camera. Similarly, the fiber optic input cable can have a second fiber optic operatively interconnected with a second input of the second camera for taking in spectral data and/or conveying it to the second camera.
The hot end of the fiber optic input cable associated with the ignition detection system utilized by the second aspect is generally disposed at least within an optically effective distance of the ignited fuel (usually, but not limited to, the exhaust plume or the ignited fuel in the combustion chamber) of the engine. In one embodiment, this optically effective distance is generally no more than about 10 feet. Some embodiments have the hot end of the fiber optic input cable actually positioned within (but not in contact with) an exhaust nozzle of the engine. Other embodiments have the hot end of the fiber optic input cable positioned within (but not in contact with) a combustion chamber of the engine. In one embodiment, the hot end of the fiber optic input cable may be separated from direct, physical contact with the launch vehicle by a distance of about 2 inches up to about 10 feet.
The hot end of the fiber optic input cable of the second aspect may be confined in a protective housing. An exemplary protective housing may be a steel receptacle having a window. Ideally, the window of such a protective housing is designed and configured to enable electromagnetic spectra to reach the hot end of the fiber optic input cable. Exemplary window materials generally include, but are not limited to, glass, quartz, sapphire, and zirconia. Other appropriate protective housings may be utilized as long as they do not significantly inhibit the hot end of the fiber optic input cable from receiving and/or conveying spectral data relating to the subject engine ignition. Generally, each of the various features discussed herein in relation to one or more of the described aspects of the present invention may be utilized by this second aspect of the present invention as well, alone or in any combination.
A third aspect of the present invention is embodied in a launch system having a camera assembly, a control assembly, and a launch vehicle that includes at least one engine. The camera assembly of the launch system generally functions to at least assist in detecting electromagnetic spectra. The camera assembly generally includes a fiber optic input cable which can have an attachment end optically connected to the camera assembly and a hot end positioned opposite the attachment end and disposable at least generally toward the engine(s). The control assembly may be operatively interconnected with the camera assembly. This control assembly is at least generally programmed with a first predetermined threshold associated with first electromagnetic spectra and a second predetermined threshold associated with second electromagnetic spectra. In addition, the control assembly is at least generally programmed with a first time threshold associated with a first time parameter in which at least one of the first and second thresholds should be reached.
Various refinements exist of the features noted in relation to the subject third aspect of the present invention as well. Further features may also be incorporated in the subject third aspect of the present invention. These refinements and additional features may exist individually or in any combination. The first electromagnetic spectra may include a wavelength range of about 200 nm to about 700 nm. Similarly, the second electromagnetic spectra may include a wavelength range of about 700 nm to about 300,000 nm. In some embodiments, one or both the first and second electromagnetic spectra may include a single, individual wavelength. It may, however, be appropriate that some embodiments of the subject third aspect have one or both first and second electromagnetic spectra outside the above-disclosed ranges.
The first time threshold, in the case of the third aspect, may generally refer to an acceptable time duration between when the first and second predetermined thresholds should be reached. In one embodiment of the third aspect, this acceptable time duration may range from about 100 milliseconds up to about 3 seconds. In another embodiment, this acceptable time duration may be no more than about 10 milliseconds. However, it may be appropriate that yet other embodiments of the subject third aspect may exhibit an appropriate first time threshold outside those disclosed above. Then again, the first time threshold of the third aspect may generally refer to an appropriate window in time, with respect to lift-off/take-off (i.e., Txe2x88x920) of the launch vehicle, in which the first electromagnetic spectra may be monitored to determine if the first predetermined threshold has been reached. Additionally or alternatively, the first time threshold of the third aspect may generally refer to an appropriate window in time, again with respect to lift-off/take-off (i.e., Txe2x88x920) of the launch vehicle, in which the second electromagnetic spectra may be monitored to determine if the second predetermined threshold has been reached. With regard to the first time threshold, the appropriate window(s) in time for one or both the first and second predetermined thresholds may generally depend upon, amongst other factors, the type of engine(s) utilized in the launch vehicle. Generally, each of the various features discussed herein in relation to any aspect of the present invention may be utilized by this third aspect of the present invention as well, alone or in any combination.
A fourth aspect of the present invention is embodied in a method of operating an engine (e.g., a rocket engine). The method generally includes initiating an ignition sequence that includes at least a first ignition stage and a second ignition stage for an engine. The method further includes monitoring first and second ignition stage electromagnetic spectra at least during a time corresponding with the first and second ignition stages, respectively. The first ignition stage electromagnetic spectra is generally monitored to determine if it reaches a first predetermined threshold. Correspondingly, the second ignition stage electromagnetic spectra is generally monitored to determine if it reaches a second predetermined threshold. xe2x80x9cReachesxe2x80x9d in relation to the first and second predetermined thresholds again generally encompasses meeting a certain value, exceeding a certain value, or both. In the event that the second predetermined threshold is not reached within a predetermined time of the first predetermined threshold being reached, the ignition sequence is generally terminated.
Various refinements exist of the features noted in relation to the subject fourth aspect of the present invention. Further features may also be incorporated in the subject fourth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. Generally, the various features discussed above in relation to any of the aspects of the present invention may be utilized by this fourth aspect, individually or in any combination.
A fifth aspect of the present invention relates to a system and method for checking the health of an ignition detection system. Herein, the xe2x80x9chealthxe2x80x9d of a system generally refers to whether or not the system is functioning appropriately. So, checking the health of the ignition detection system may include (but is not limited to) determining if optical data is being appropriately conveyed through the ignition detection system, and determining if the optical data is being appropriately and/or accurately converted to electrical signals indicative of the optical data. The health check system of this fifth aspect generally includes a health check panel that is electrically interconnected with a test lamp assembly. This test lamp assembly generally includes a first lamp and a test fiber optic cable that is optically interconnected with the test lamp assembly and that has a hot end opposite an attachment end that is optically interconnected with the test lamp assembly for conveying electromagnetic spectra emitted from the first lamp toward an associated ignition detection system.
Various refinements exist of the features noted in relation to the subject fifth aspect of the present invention. Further features may also be incorporated in the subject fifth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. For example, in one embodiment of the fifth aspect, the health check system may be an integral component of an associated ignition detection system. However, in another embodiment, the health check system may be separate and distinct from an associated ignition detection system. In any event, the health check panel of the health check system may be electrically interconnected (i.e., capable of sending/receiving electrical signals between first and second components) with the test lamp assembly via a wire that is capable of conducting electrical signals. This wire may be made up of any appropriate conducting material (e.g., a metal such as copper) and may have an insulating material (e.g., rubber or plastic) surrounding at least portions of the conducting material.
In the cases this fifth aspect, the first lamp of the test lamp assembly, generally upon being activated due to an electrical signal from the health check panel, may emit/give off light rays (i.e., electromagnetic spectra) that coincide with an above-described predetermined threshold (e.g., first and/or second predetermined thresholds) of an associated ignition detection system. In other words, upon illumination of this first lamp of the test lamp assembly, the health check system may generally provide electromagnetic spectra indicative of at least a stage of an appropriate engine ignition. However, the first lamp of another embodiment of the fifth aspect may emit photons that may not be indicative of at least a stage of an appropriate engine ignition.
The test lamp assembly of fifth aspect of the present invention may also include a second lamp. Generally upon being activated due to an electrical signal from the health check panel, the second lamp may emit/give off light rays (i.e., electromagnetic spectra) that coincide with another of the above-described predetermined thresholds (e.g., first and/or second predetermined thresholds) of an associated ignition detection system. In other words, upon illumination of this second lamp of the test lamp assembly, the health check system may generally provide electromagnetic spectra indicative of at least a stage of a positive/desired engine ignition. Accordingly, one embodiment of the fifth aspect may exhibit the first test lamp emitting electromagnetic spectra indicative of a first predetermined threshold of the associated ignition detection system, and the second lamp emitting electromagnetic spectra indicative of the second predetermined threshold of the associated ignition detection system. As with the first lamp of the health check system of the fifth aspect, the second lamp of another embodiment may emit photons that may not be indicative of at least a stage of an appropriate engine ignition. In any event, another embodiments of the fifth aspect of the present invention may include more than 2 test lamps (e.g., 3,4,or 5 test lamps).
Accordingly, a method of using a health check system of the fifth aspect may generally including issuing one or more electrical signals from the health check panel to the test lamp assembly. In response to receiving the electrical signal(s), the test lamp assembly may issue one or more optical signals (i.e., light) that travel away from the test lamp assembly toward the associated ignition detection system. With regard to these optical signals, the test lamp assembly may emit (i.e., give off) optical signals within a desired first range that is to be detected by the ignition detection system. In one embodiment, the test lamp assembly may emit electromagnetic spectra that reach a first predetermined threshold of the ignition detection system. The test lamp assembly may also emit electromagnetic spectra within a desired second range that is to be detected by the ignition detection system. Thus, the test lamp assembly may generally emit electromagnetic spectra that reach a second predetermined threshold of the ignition detection system. In one embodiment, the health check system may be configured to give off a first optical signal at a first time (or during a first duration of time) prior to giving off a second optical signal (at least generally different in wavelength from the first optical signal) at a second time (or during a second duration of time). In other words, the health check system of this fifth aspect may be configured in any appropriate manner that enables the health check system to mimic a successful/appropriate engine ignition with regard in one or both wavelength and timing of the particular ignition. That is, the health check system of this fifth aspect is generally designed to provide the associated ignition detection system with an artificial positive indication of an appropriate engine ignition.